1.6 μm AlxGayIn1-x-yAs/InP多重量子井雷射結構材料的能隙調整

本研究探討量子井微擾技術在延長諧振腔雷射元件中的應用。主要目的是用來改善材料或元件特性及降低波導損失。在均勻的結構中，主動區與被動區能隙值相同，導致由主動區激勵放射出的光波，會在被動的波導區被吸收造成很大的光損失。利用量子井微擾技術，改變量子井能帶結構，使被動區在能隙變寬後，大幅減少了傳輸的光損失，極有利於高性能元件的製成。本研究小組設計出的InGaAlAs/InP的多重量子井GRINSCH結構，採用介質遮蔽式微擾技術，於主動區與被動區表面，分別以厚度為200 nm的TiO2及SiO2的介質薄膜為遮蔽層。因為SiO2-InP間的熱膨脹係數差值較TiO2-InP大提供較多空缺，使III族原子的混擾程度增加；相對的，TiO2薄膜的遮蔽則會抑制混擾的進行，其能隙在製程中變化很小。另一方面，在抑制混擾方面，由於Ge熱膨脹係數與InP基板相近，加入厚度30 nm的Ge中介層於樣品與SiO2介質薄膜間，實驗結果顯示，此適當厚度的Ge中介層可完全抑制量子井的混擾。本研究藉由光激發光譜(PL)與表面電阻係數量測，來分析雷射結構在量子井微擾後光電特性的變化。在退火溫度740℃加溫60秒的處理後，量子井結構主動區SiO2薄膜遮蔽與Ge中介層的樣品，出現最大幅度33 nm的紅移。另一批樣品，其主動區表面用TiO2遮蔽而被動區表面用SiO2遮蔽，可得到29 nm的能隙差值( )。此外，在電性方面上述處理後與控制樣品比較，混擾加強區有 Ω-cm，而混擾抑制區有 Ω-cm的電阻係數差異。我們發現退火微擾時的溫度越高，表面電阻係數也越大，意指表面層經原子混擾後，表面狀況及電性有微幅變差的現象。

關鍵字

量子井微擾； AlGaInAs/InP ；量子井雷射；調整能隙；介質遮蔽式微擾

並列摘要

The applications of quantum-well disordering technique to photonic devices have been studied in this work. This technique is utilized for reducing the waveguide losses and for improving the device performances. For the homogeneous microstructures, the bandgaps of active and the passive regions are the same, the emitting light source from the active section generally will suffer significant optical losses. By using quantum-well disordering techniques, the bandgap of the passive waveguide section can be widen resulting in low transmission loss, which is vitally important for the fabrication of high-performance optical devices. With multiple-quantum-well InGaAlAs/InP GRINSCH structures designed by our group, dielectric cap disordering was implemented onto the active and passive sections by depositing 200-nm thick TiO2 and SiO2 films, respectively. It was investigated that the SiO2 cap accommodates much more vacancies than that of the TiO2 cap, so the SiO2-capped region would experience enhanced quantum-well disordering, while the TiO2-capped region would suppress the disordering. Moreover, Ge interlayer was deposited in between the SiO2 cap and the InP surface to reduce the strain between them, nearly complete suppression of the disordering was found for this sandwiched capping microstructure. In order to quantitatively analyze the change in material properties after the disordering, photoluminescence(PL) and four-point probes were used. On the disordering condition at 740℃ for 60 seconds, for example, the differential PL red shift was 33 nm for the samples with Ge interlayer, compared to a blue shift of 29 nm for the sample using TiO2 and SiO2 caps. On the other hand, the increases in electrical resistivity were Ω-cm and Ω-cm for the SiO2 capped and the TiO2 capped regions respectively, compared to Ω-cm for the control sample. We found that the surface morphology and electrical properties of the disordered samples experienced slight degradation after the quantum-well disordering.

並列關鍵字

Quantum well disordering ； InGaAlAs/InP ； Quantum well lasers ； Bandgap engineering ； Dielectric-cap disordering

參考文獻

[1] H. Ishii, Y. Tohori, M. Yamamoto, T. Tamamura, and Y. Yoshikuni, “Modified multiple-phase-shift super-structure-grating DBR lasers for broad wavelength tuning,” IEEE Electronics Letters, 7TH vol. 30, no. 14, July, 1994, pp. 1141-1142.

[2] F. Capasso, “New multilayer and graded gap optoelectronic and high speed devices by band gap engineering,” Surf. Sci., 142, 1984, pp. 513-528.

[3] E. H. Li and B. L. Weiss, “Bandgap engineering and quantum wells in optoelectronic devices,” Appl. Electronics & communication engineering Journal, vol. 3, no. 2, April 1991, pp. 63-79.

[5] L. Eldada et al., “Hybrid integrated optical source subsystem on a chip,” Proc. SPIE, vol. 89, 2002, pp.4654.

[8] S. Kim and V. Gopalan, “Strain-tunable photonic band gap crystals,” Applied Physics Letters, Vol.78, 2001, pp.3015-3017.

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1.6 μm AlxGayIn1-x-yAs/InP多重量子井雷射結構材料的能隙調整

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